PURPOSE: A maintenance method of a thruster for a drillship is provided to prevent damage to the parts of a thruster caused by a collision. CONSTITUTION: A maintenance method of a thruster for a drillship is as follows. A thruster (110) is lifted by a strand jack unit (300) and is detached from a hull (100). The strand jack unit is arranged on an upper deck (130) during an installation work or a maintenance work. The thruster is lifted to the upper area of the upper deck through a vertical penetration path (120) to be extended to the upper deck. When the thruster is lifted up, a guide bar (200) formed on the inner wall of the vertical penetration path guides the thruster.
